1. Field of the Invention
This invention relates to curable epoxy resins having increased resistance to solvents.
2. Prior Art
Epoxy resins constitute a broad class of polymeric materials having a wide range of physical characteristics. The resins are characterized by epoxide groups which are cured by reaction with certain catalysts or curing agents to provide cured epoxy resin compositions with certain desirable properties. It is known to use N,N' ethylene bis(maleamic acid) in photohardenable resin compositions. Also, epoxy resins have been hardened with polycarboxylic acids and diaminodiphenylcarboxylic acid. More generally, carboxylic acid from formic to salicylic were suggested as hardening accelerators. References to these prior art curing systems and accelerators are disclosed in the following places:
CA 84, 67870m, PA1 CA 83, 165100j, PA1 U.S. Pat. No. 3,937,751, PA1 German No. 2,100,275, PA1 U.S. Pat. No. 3,963,796, and PA1 Lee & Neville, Handbook of Epoxy Resins, McGraw-Hill, 1967, 10-11.
We have disclosed in prior patents curing systems which included succinimides. These succinimides are formed by the condensation of two moles of polyoxyalkylenepolyamines with maleic anhydride, for example. See U.S. Pat. Nos. 4,115,361 and 4,146,701, for example.
From the prior art, it was not apparent that the particular combination of a vicinal polyepoxide and a curing amount of aromatic polyamines with a condensation product of about two moles of maleic anhydride with one mole of a polyoxyalkylene diamine of 400 molecular weight or less would give an epoxy resin having generally good properties and superior solvent resistance.